Geograph - photograph every grid square

This is the machinery that operated one of the four lock gates and is variously ascribed to the 1880s or 1902. It consists of a double acting hydraulic cylinder connected to the gate via a crosshead and connecting rod. The operating mechanism is on the left and consists of a single lever for open and close. A very simple interlock system ensures that it can't overstroke or be started in the wrong direction. Three of the gates have this arrangement but the fourth has the added refinement (?) of a device that seems to be able to alter the hydraulic pressure between 390 and 760 psi. The nominal pressure of the London system was 750 psi.